Pearlite vs. Bainite

Pearlitenoun

A two-phased lamellar structure composed of alternating layers of alpha ferrite and cementite that occurs in some steels and cast irons, having a pearlescent appearance.

Pearlitenoun

(mineral) perlite

Pearlitenoun

A glassy volcanic rock of a grayish color and pearly luster, often having a spherulitic concretionary structure due to the curved cracks produced by contraction in cooling. See Illust. under Perlitic.

Pearlitenoun

a lamellar mixture of cementite and ferrite formed during the cooling of austenite; a micro-constituent of steel and cast iron

Pearlite

Pearlite is a two-phased, lamellar (or layered) structure composed of alternating layers of ferrite (87.5 wt%) and cementite (12.5 wt%) that occurs in some steels and cast irons. During slow cooling of an iron-carbon alloy, pearlite forms by a eutectoid reaction as austenite cools below 723 °C (1,333 °F) (the eutectoid temperature).

Bainitenoun

(metallurgy) A microstructure of steel consisting of needle-like particles of cementite embedded in a ferrite matrix.

Bainite

Bainite is a plate-like microstructure that forms in steels at temperatures of 125–550 °C (depending on alloy content). First described by E. S. Davenport and Edgar Bain, it is one of the products that may form when austenite (the face-centered cubic crystal structure of iron) is cooled past a temperature where it no longer is thermodynamically stable with respect to ferrite, cementite, or ferrite and cementite.